How to add MD5 to the name of apk with Gradle

For our naming convention, we need to add in the end of the apk name the MD5 of the file. I tried to use this fun

static def generateMD5(final file) {
MessageDigest digest = MessageDigest.getInstance("MD5")
file.withInputStream(){is->
    byte[] buffer = new byte[8192]
    int read = 0
    while( (read = is.read(buffer)) > 0) {
        digest.update(buffer, 0, read);
    }
}
byte[] md5sum = digest.digest()
BigInteger bigInt = new BigInteger(1, md5sum)
return bigInt.toString(16).padLeft(32, '0')

and in the application variant task

android.applicationVariants.all { variant ->
    variant.outputs.all { output ->
        output.outputFileName = "MyApp v${variant.versionName}-${generateMD5(output.outputFile)}.apk"
    }
}

The problem is that the APK file is not created in this task, so where i should modify the filename?